The present invention is related to xe2x80x9cActive System and Method For Detecting Harmonics of RF Broadcast Station Survey Signalsxe2x80x9d, by David G. Worthy, which is incorporated by reference herein.
The present invention relates generally to the identification of radio stations to which radio tuners are tuned. More specifically, the present invention relates to the detection of the harmonics of survey signals, from a remote location, to identify the radio stations to which tuners are tuned.
The commercial broadcast industry and businesses which advertise through the radio frequency (RF) broadcast media need to know the sizes of audiences which are tuned to particular stations relative to other stations at particular times. This need has been met primarily through the use of verbal or written audience participation surveys. With respect to radio, a majority of the listening occurs in automobiles. A problem with written surveys is that listeners cannot practically make a record of their listening tendencies while driving.
In order to make a record of listening tendencies while driving, passive electronic RF monitoring equipment has been used to remotely identify the stations to which tuners may be tuned. Generally speaking, audiences"" radio tuners use predetermined signals, such as local oscillator signals, that are related to the frequencies of the respective stations currently being tuned in. The local oscillator signals are broadcast or otherwise emitted from the tuners as very weak signals that sensitive monitoring equipment can detect. The passive monitoring equipment identifies the radio stations to which tuners are tuned by detecting these local oscillator signals.
This remote monitoring technique is desirable because it does not require cooperation from an audience, hence reducing or eliminating a host of inaccuracies and costs associated with audience participation surveys. Furthermore, large sample sizes may be monitored at low cost relative to audience participation survey techniques.
Typically, prior art passive monitoring systems call for the local oscillator signals to be well above the level of background electronic noise in the area at which the remote monitoring is to occur. One primary source of background electronic noise, or interference, is from the radio stations themselves because the radio stations broadcast near in frequency to the desired local oscillator signal, and with much higher power.
The background electronic noise may cause local oscillator signals at some frequencies to be more readily detectable than other frequencies leading to station bias in favor of stations whose related local oscillator signals may have a lower level of background noise. One attempt to compensate for this station bias is to tune the monitoring equipment to the radio station or frequency with the lowest amount of signal to noise ratio in order to equalize the detection of the noisiest local oscillator signal with the detection of the other less noisy oscillator signals. Unfortunately, such a strategy results in the reduced sensitivity of the monitoring equipment and a reduced number of incidences that a radio station is identified, or counted, through the detection of the corresponding local oscillator signal.
In addition, other types of interference will affect the prior art passive monitoring systems. For example, interference from intermittent transmissions from radio stations, television stations, airports, and so forth may be erroneously counted by the monitoring equipment. Consequently, significant xe2x80x9cpostxe2x80x9d data integrity checking is employed to eliminate such erroneous counts from the record. Post data integrity checking undesirably drives up the costs of the survey technique and increases the potential for creating error in the survey record.
An active electronic RF monitoring system has also been used to remotely identify the stations to which tuners may be tuned. The active system broadcasts an RF survey signal which is related to an RF carrier signal, or radio broadcast signal. The RF survey signal is configured to cause a radio tuner to emit an audio echo signal from its corresponding speaker. Simultaneously, the audio echo signal is electromagnetically radiated from the radio tuner when the tuner is tuned to the radio broadcast signal related to the RF survey signal. The active monitoring equipment identifies the radio stations to which tuners are tuned by detecting the electromagnetically radiated audio echo signal. Unfortunately, the audio echo signal may be detected by some survey participants as interference on the radio station.
Accordingly, it is an advantage of the present invention that a system and method for remotely identifying RF broadcast stations in the presence of significant background interference are provided.
It is another advantage of the present invention that the system and method identify RF broadcast stations by detecting the harmonics of survey signals.
It is another advantage of the present invention that the system and method remotely obtain audience survey data in a manner that does not interfere with the RF broadcast signals.
It is yet another advantage of the present invention that post data integrity checking is substantially reduced through the detection of the harmonics of the survey signals.
The above and other advantages of the present invention are carried out in one form by a remote audience survey method for identifying radio stations to which tuners are tuned, the tuners having predetermined signals emitted therefrom, and the predetermined signals being associated with the radio stations. The method calls for selecting one of the predetermined signals associated with one of the radio stations, the one predetermined signal exhibiting a fundamental frequency. The method further calls for receiving a second signal, detecting a harmonic of the fundamental frequency within the second signal, and determining that one of the tuners is tuned to the radio station in response to the detecting operation.
The above and other advantages of the present invention are carried out in another form by a remote audience survey system for identifying a radio station to which a tuner is tuned, the tuner having local oscillator (LO) signals emitted therefrom. The system includes a controller configured to select one of the LO signals associated with the radio station, the one LO signal exhibiting a fundamental frequency. An antenna is configured to receive a second signal. A receiver is in communication with the antenna the controller. The receiver is configured to detect a harmonic of the fundamental frequency within the second signal to determine that the tuner is tuned to the radio station.